1. Field of the Invention
This invention relates to a device electronic in nature with no moving parts that accomplishes the ignition of a fuel air mixture in an internal combustion engine, and in particular to a device that determines the correct time to fire the fuel air mixture so that a predetermined and set advance firing angle (AFA) may be applied to the firing of a spark plug which is dependent on the speed of the engine. The correct time for firing the spark plug at the desired AFA as well as the determination of the speed of the engine is determined with each firing cycle of the cylinder and this information is used on the next firing cycle of the cylinder. The invention accomplishes the above with the use of hardware that is solely dedicated to performing the above tasks as opposed to units that use a microprocessor and associated software.
2. Prior Art
Ignition devices for the firing of a spark plug in an internal combustion engine are well know in prior art and are widely used. This invention seeks to provide a device which has a regulated spark plug firing voltage which is independent of the speed of the engine so as to improve the reliability of the firing of the spark plug. This invention seeks to improve the speed pick up or acceleration of an internal combustion engine that utilizes electronic ignition devices that utilize speed averaging techniques for the determining of the speed of the engine and for the setting of the AFA at which the spark plug is fired. The improvement is accomplished by determining the speed of the engine and the AFA to be applied to the firing of the spark plug with each fuel air compression stroke of the cylinder, and applying this to the next firing cycle of the cylinder. This thus affords a much faster speed pick up of an engine.
This invention seeks to provide an improvement over ignition devices that use a mechanical means of changing the AFA at which the spark plug is fired. A mechanical means of changing the AFA of the spark plug firing normally means moving a sensor such as a Hall sensor with relationship to a moving permanent magnet (PM) which is normally mounted to the rotating shaft of an engine. Movement of the sensor is typically done by mechanically coupling it to the throttle of the engine. Having a device such as this invention that has a single nonmoving sensor such as a Hall sensor for the sensing of a passing reference point in the engine's firing cycle means a greater ease of installation and reliability as there are no moving parts which may wear out or break. A further advantage of this invention is that it allows the user of the invention to change the AFA at which the spark plug is fired while the engine is running at full throttle or above a reference speed called the idle Threshold Speed (ITS) of the engine by the adjusting of a potentiometer. The AFA of the spark plug is set to 0 degrees below the ITS and it is independent of the above said potentiometer. This allows for a much smoother idle of the engine. With an ignition device that uses a mechanical means of changing the AFA of the spark plug, changes that are made to the AFA of the spark plug firing at the full throttle setting of the engine have a high probability of also affecting the AFA of the spark plug firing at the low throttle position of the engine as well. If the same AFA firing of the spark plug is to be maintained at the low throttle setting when the high throttle setting of the AFA of the spark plug firing has been changed, then fundamental changes to the movement of the Hall sensor will have to be made which may prove difficult.
A further advantage of this invention over that of an ignition device that has an AFA that is mechanically controlled is that it ensures that the AFA firing of the spark plug will not be advanced too rapidly or by not too much for the given current speed of the engine as the AFA applied to the firing of the spark plug is dependent on the speed of the engine. Rapid advances of AFA to the firing of the spark plug can cause too early a firing of the fuel air mixture and this can cause the engine speed to be slowed and in severe cases it can cause the engine to be stopped as well as cause excessive vibration of the engine to occur.
Furthermore this invention seeks to provide a greater safety aspect for the user of internal combustion engines that are going to be hand started, such as those engines employed in chain saw applications or in model aircraft applications. An engine whose AFA firing of the spark plug is controlled by mechanical coupling to the throttle may be started with the AFA firing of the spark plug at greater than 0 degrees of AFA. If during starting of an engine with this type of mechanical AFA control, the user does not put enough energy into rotating the crank shaft of the engine on the fuel air compression stroke of the engine to overcome the additional pressure of the firing fuel air mixture so that the piston goes beyond top dead center of the compression stroke of the engine, the engine will backfire with a strong possibility of hurting the person starting the engine. This is especially true of engines that are employed in model aircraft applications as the user is probably hand flipping the propeller and a backfire may hurt the user's hand, and in severe cases may cut it and or remove it. The propeller may even come off as often does happen and strike the user or bystanders.
Furthermore this invention seeks to provide an advantage over ignition units for internal combustion engines that are computer controlled through software. The advantages are that this invention causes less electromagnetic radiation to be emitted thus resulting in less radio interference which is desirable in the operation of radio control model aircraft. Less electromagnetic radiation emissions is a result of having the circuit elements of the invention transition once per compression stroke of the fuel air mixture of the cylinder whereas computer controlled ignition units have internal signals changing many times per compression stroke of the fuel air mixture of the cylinder. A further advantage of having a dedicated piece of electrical hardware to control the AFA firing of the spark plug is that it will be able to perform this function much faster than a software controlled ignition unit and with a greater AFA accuracy possible at the higher engine speeds. A further object of this invention is to provide an advantage over those units that are commonly known as 2 fixed sensor or 2 fixed position ignition devices where the AFA applied to the firing of the spark plug is switched between these 2 points. The main advantage of this invention over the just said ignition device is that the top engine speed AFA firing of the spark plug is electronically changeable by mean of a potentiometer as opposed to being fixed. To change the AFA of the firing of a spark plug of a 2 sensor position ignition device one has to mechanically alter the relative position of the high speed AFA sensor. This may prove difficult to do if the engine is running due to safety aspects. Engines normally used in model airplane applications have the sensors placed on the shaft of the engine in close proximity to the propeller therefore making adjustments difficult if the propeller is rotating. Also with a 2 position ignition device there are only 2 set points for the AFA of the firing of the spark plug. The disclosed invention changes the AFA firing of the spark plug depending on the speed of the engine, exact details of how this is accomplished is covered in the detailed description of the invention,